The White House scrambled Monday to reassert its "zero tolerance" policy after a key Department of Homeland Security official said Border Patrol agents had stopped enforcing it.

"We're not changing the policy," White House press secretary Sarah Huckabee Sanders said at the daily briefing. "We're simply out of resources. And at some point, Congress has to do what they were elected to do."

"We're not prosecuting those parents," McAleenan said. He cited as the reason President Donald Trump's executive order last week requiring parents to be detained with their children, after an earlier policy of separating parents and children prompted a national uproar.

McAleenan said the suspension was temporary, but he didn't say when prosecutions would resume.

Several DHS officials have said privately that the president's order made it impossible to continue zero tolerance, but McAleenan was the first to say so publicly.

The White House and the Justice Department continue to insist that zero tolerance is still in effect, even as it becomes increasingly evident that it's broken down.

"If we refused to prosecute these adults for illegal entry — as many of our critics want us to do — that would be a disservice to the people of this country," Attorney General Jeff Sessions said in a speech Monday in Reno, Nevada.

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But the Justice Department can't prosecute parents who cross the southern border with children if Border Patrol doesn't refer them for prosecution.

Border Patrol's suspension of those referralsreinstates what Trump has publicly criticized as a “catch and release“ policy for migrant families.

Trump's executive order barring the separation of parents and children rendered the zero-tolerance policy unenforceable almost immediately because there wasn't sufficient detention space to house the thousands of family members who arrive at the border each month.

U.S. Immigration and Customs Enforcement operates three family detention facilities with a total of 3,326 beds, according to a 2018 report to Congress. More than three-quarters of those beds were filled as of June 20, according to the agency.

In addition, federal officials cannot hold migrant children in detention for more than 20 days under the 1997 Flores settlement agreement,which established basic standards for the treatment of minors.

The Justice Department last week asked U.S. District Court Judge Dolly Gee to revise the Flores agreement to allow children to be detained indefinitely along with their parents. But Gee, an Obama appointee, is considered unlikely to grant the request. A ruling could come as early as this week.

The suspension of zero tolerance leaves the Trump administration with no clear plan to move forward.

CBP spokesman Andrew Meehan said in a written statement that the agency took “temporary action“ so that Congress can pass legislation that deals with family separation. “We encourage them to act,” he said.

But any such action is a very long shot. Republican leaders in the House postponed a planned vote last week on a compromise immigration bill that would tackle much of Trump’s agenda while giving so-called Dreamers who arrived in the U.S. as children a path to citizenship.

A separate House vote on a hard-line immigration bill from Rep. Bob Goodlatte (R-Va.) failed Thursday on a 193-231 vote.

The executive order, assembled hastily at Trump’s request on the morning of June 20, sparked tensions among agencies that struggled to enact it, POLITICO reported last week.

For instance, the order didn’t make clear whether the administration would seek to reunite children and families previously separated under the zero-tolerance initiative.

A spokesman for the Health and Human Services Department’s Administration for Children and Families said initially that no special procedures would be taken to reunite separated children with their parents. A different official later walked back that statement, but made no promise that all families would be reunited.

On Saturday evening, the administration said it had reunited 522 separated children with parents or guardians and outlined efforts to reconnect families.

The decision to suspend zero tolerance may ease a growing housing crunch for unaccompanied minors.

Under the policy, adults were referred for federal prosecution under illegal entry and re-entry statutes. Children traveling with them were then placed in the care of the Office of Refugee Resettlement.

The separated children flooded the shelter system, which held nearly 12,000 children last week.

To create additional shelter capacity, the administration opened a “tent city” earlier this month near a port of entry in Tornillo, Texas.

But the contract for that facility will end July 13, an HHS spokesperson told a local ABC affiliate. The federal government has not made a decision on whether to extend the contract, according to an ACF spokesman.

The tent city has come under scrutiny by immigration advocates who question whether it meets Flores standards to house minors.

Liberal lawmakers and advocates descended on the shelter last week to protest zero tolerance, calling for the release of children separated from their families.

The Trump administration could soon have more beds for children on the way. HHS has asked the Defense Department to determine whether it can provide 20,000 temporary beds for unaccompanied minors from July through the end of the year, according to a notification sent to congressional offices last week.

At the White House press briefing Monday, Sanders was pressed on what additional resources the administration was seeking to deal with migrants at the border.

"We're looking at every option available, we've asked the Pentagon to help with additional space,” she said. “But a lot of that will depend on our ability to stop people coming into the country illegally."